1. Field of the Invention
The present invention relates to a synthetic resin pelletizing machine or pelletizer that shapes by extruding a raw material, such as synthetic resin powder, granules or pellets, into a continuous form of extrudate and, after cooling the continuous extrudate, cuts off the same into small pellets.
2. Description of the Prior Art
In the synthetic resin molding industry, it is a customary practice to mix a plurality of synthetic resin materials of different properties to form a molded product of desired characteristics. In this instance, if the mixing is not homogeneous, the final product has undesired characteristics. To avoid this problem, as disclosed in Japanese Patent Publication No. 63-32604, each of various synthetic resins are separately supplied to an extrusion unit in which each resin is separately melted and separately extracted as a strand into a cooling water bath. The cooled strand is cut into fine granules or pellets. The fine pellets thus produced are then mixed with similar pellets of different kinds of synthetic resins to form a molded article.
In general, the conventional pelletizing machine of the type concerned is, as also mentioned in the above-referenced Japanese patent publication, a large-sized machine to cope with the mass-production system. Accordingly, the extrusion unit incorporated in such a large-sized pelletizing machine is necessarily large in size, and taking the maintenance into account, it is composed of a horizontal-type extrusion unit having an extrusion cylinder horizontally mounted on a machine frame.
The known pelletizing machine of the foregoing construction occupies a large space in a horizontal direction and, hence, uses the space inefficiently. In addition, the known pelletizing machine is not adaptable to the multi-product, small-quantity production system which has recently been required for various molded articles. An attempted use of the conventional pelletizing machine in the multi-product, small-quantity production system would produce an excessive stock of molded articles, requiring a complicated stock control operation. Accordingly, there is a keen demand for a pelletizing machine which is compact in size and readily adaptable to the multi-product, small-quantity production system. Furthermore, since the raw resin is supplied to the horizontal-type extrusion cylinder at right angles to the axis of an extrusion screw, the raw resin is likely to become clogged at an inlet of the extrusion cylinder. In addition, the strand, as it is extruded from the horizontal-type extrusion cylinder into a cooling bath, is subjected to a lateral bending force which will exert negative influence on the quality of the pellets produced from the extruded strand.